Semiconductor spintronics aims to add novel functionality to electronic devices by utilizing the spin degree of freedom. Group-IV semiconductors are of particular interest due to the potential compatibility with established silicon technologies, and germanium has shown favorable properties related to magnetic doping. One of the main challenges for germanium-based spintronics is to achieve efficient spin injection from ferromagnetic (FM) metal contacts into germanium. In addition, metal/n-germanium contacts have a strong Fermi level pinning problem.
Accordingly, there is a need to resolve the conductivity mismatch problems of FM/n-Ge contact for spin injection and relieve the problem of strong Fermi level pinning by insertion of an insulator layer between the ferromagnetic metal layer and germanium layer.